Visually evoked blood flow responses in the posterior cerebral artery: Effects of age and stimulus conditions on the response amplitude

Using transcranial Doppler sonography we assessed the effects of intermitte nt light stimulation with 10 Hz on the blood flow velocity in the posterior cerebral artery. The effects of age and sex on the amplitude of the visual ly evoked flow response (VEFR) were evaluated in 30 healthy volunteers. The study further addressed the influence of stimulus duration and habituation on the response amplitude. During stimulation periods of 60 s the mean blo od flow velocity increased by 13.8 +/- 4.8% without significant side-to-sid e differences. No sex-related differences were found, but the response ampl itude decreased significantly with age (r = -0.344, p < 0.001). There was a negative relationship between the response amplitude and the duration and number of applied stimulation periods. To our knowledge, this study is the first to present normative data for visually evoked blood flow responses to photic stimulation. Regarding diagnostic application of VEFRs effects of h abituation and the age-dependency of the response amplitude should be taken into consideration.